2D Game/App, Core Graphic

Hi there,
I'm starting using the SDK, and I would realize a pong clone app using Core Graphic, for draw paddles, ball and score.
I read the documentation and trying draw path, rect and other things using Core Graphic and it's all ok.
Now my problem is that I need a cycle (60fps?) where I put the code for update coordinates of the paddles and ball and after it redraw all with the new data.
I always use "Utility Application" template and then import Core Graphic framework to the project.